KABUL, AFGHANISTAN — Afghan Presidential candidate Abdullah Abdullah on Tuesday said he received calls from President Barack Obama and U.S. Secretary of State John Kerry after he refused to accept the preliminary result of the vote citing fraud.

Abdullah told thousands of supporters at a gathering in Kabul that Kerry would be flying to the Afghan capital this Friday for meetings and help defuse the crisis.

State Department officials accompanying Kerry in Beijing declined to comment on his travel plans.

He told his supporters that the results of the election were fraudulent, but asked them to give him a few more days to negotiate.

“We denounce and do not accept the results of fraudulent vote. I assure you people of Afghanistan that I will sacrifice for you, but I will never accept a fraudulent government,” he told his supporters, many angry over the result. “We announce that only the government elected through clean votes will come to power.”

The Afghan Independent Election Commission released preliminary election results Monday showing former finance minister Ashraf Ghani Ahmadzai well in the lead for the presidency but said no winner could be declared because millions of ballots were being audited for fraud.

Preliminary results announced Monday showed that Ahmadzai had about 4.5 million votes, or 56 percent, while Abdullah had 3.5 million votes, or 44 percent, according to the commission. Turnout was more than 50 percent.

The turmoil came as violence escalated around the country.

An Afghan official says that at least 16 people, including four Czech soldiers, were killed Tuesday in a suicide attack near a clinic in eastern Afghanistan.

The Czech Ministry of Defense said Tuesday four Czech troops were killed and another was badly wounded after the blast. The ministry said it will release more details later in the day.

Wahid Seddiqi, spokesman for the provincial governor of Parwan province said the soldiers, at least 10 civilians, and two police officers were killed when a suicide bomber attacked Afghan and foreign forces near Charakar, the provincial capital.

The Taliban claimed responsibility for the attack in a statement sent to the media

The announcement came as Ahmadzai was locked in a standoff with Abdullah, who has refused to accept any results until all fraudulent ballots are invalidated. A spokesman for his campaign rejected the results and called the decision to release them “a coup.”

The election commission acknowledged that vote rigging had occurred and said ballots from about 7,000 more of the nearly 23,000 polling stations would be audited.

Abdullah charged that outgoing President Hamid Karzai, Ahmadzai and the election commission were colluding.

“President Karzai, the election commissions and Ashraf Ghani’s team are all one. They ignored us and announced the fraudulent results,” he said.

There were fears that Abdullah could ignore the result and declare victory, something he hinted at during his speech.

“People across the county call on us to announce our government and I can’t not say no to people’s wish, we don’t want civil war, we don’t want crisis. All of our lives we defended this country. We do not want crisis, we want national unity,” Abdullah said. “We don’t want separation, we don’t want civil war.”

U.S. Secretary of State John Kerry said during a visit to Tokyo that any action to seize power illegally in Afghanistan would lead to the end of U.S. financial and security support.

Kerry said suggestions of a “parallel government” in Afghanistan were a grave concern and added that he expected Afghan electoral institutions to conduct a full review of all reasonable allegations of irregularities. He said there was no justification for violence or threats of extralegal action.

“President Obama called me today saying John Kerry is coming to Kabul on Friday. President Obama and Kerry both called me this morning, promised to help us in cleaning up votes,” Abdullah told the crowd. “John Kerry phoned me before the announcement and told me that his envoys would seek a legal solution for the problems created in here.”